Determination of the Strain Influence on the InAs/InAsSb Type-II Superlattice Effective Masses

Abstract

A³B⁵ materials used for the superlattice (SL) fabrication have properties that enable the design of devices optimized for infrared (IR) detection. These devices are used in the military, industry, medicine and in other areas of science and technology. The paper presents the theoretical assessment and analysis of the InAs/InAs_1-xSb_x type-II superlattice (T2SL) (grown on GaSb buffer layer) strain impact on the bandgap energy and on the effective masses of electrons and holes at 150 K. The theoretical research was carried out with the use of the commercial program SimuApsys (Crosslight). The k·p method was adopted in T2SL modeling. Luttinger coefficients (γ₁, γ₂ and γ₃) were assessed assuming the Kane coefficient F = 0. The bandgap energy of ternary materials (InAs_xSb_1-x) was determined assuming that the bowing parameter (b_g) for the above-mentioned temperature is b_g = 750 meV. The cutoff wavelength values were estimated based on the theoretically determined absorption coefficients (from approximation the quadratic absorption coefficient). The bandgap energy was calculated according to the following formula: E_g = 1.24/λ_cutoff. The theoretical simulations allowed us to conclude that the strain in T2SL causes the E_g shift, which also has an impact on the effective masses m_e and m_h, playing an important role for the device's optical and electrical performance. The T2SLs-simulated results at 150 K are comparable to those measured experimentally.

Keywords: effective masses; infrared detectors; k·p method; type-II superlattice.